I've been wondering - is there a point when people lose faith that they're getting ROI by buying adwords? Isn't it possible that the culture may just stop givi

I've been wondering - is there a point when people lose faith that they're getting ROI by buying adwords? Isn't it possible that the culture may just stop giving money to Google at some point? And then no more aqui-hires, so no more inflated valuations, and then most of us go back to whatever we were doing before we were working at startups, right?